> At a technical level this kind of cross-site cross-pollination is quite achievable with the technical resources available to the major players concerned – supercookies, canvas fingerprinting, and global cookies acting as cross-site intermediaries all offer the possibility of breaking through a website’s sandbox.

Any idea what they're getting at here? All of them just sound like ways to uniquely identify a user.. so being generous I'll assume LinkedIn can always work out my gmail address even if I use another address to sign up.. what next, they hack my account using one of those?